This invention relates to an apparatus for manufacturing fine particles, of the particle size less than 50 microns, or more specifically ultrafine particles, of the particle size less than 1 micron, of a variety of metallic materials. More particularly, it relates to improvements of apparatuses for manufacturing metallic fine particles from any metallic material, having arc-discharging section(s) in which the material is heated and melted.
Metallic fine particles, and metallic ultrafine particles in particular, have had a lot of interest in recent years since they exhibit quite excellent properties entirely different from those of the normal metallic blocks, with respect to magnetic, optical, electrical, thermoconductive and the like properties, including reactivity and sinterability among others as are noted in particular, thus promising the possibility of utilization as excellent materials in a variety of the technical fields as in powder metallurgy, magnetics, catalysts, heat-proofing, cryogenics, welding, medicine and so forth.
However, there have as yet been no conventional apparatuses capable of manufacturing the metallic fine particles in continuous and effective mass production process, and thus keenly desired at present is the developement of such apparatuses, for the practical use as can manufacture the metallic fine particles on an industrial scale and at commercially paying costs.
Describing the further details, a couple of typical conventional apparatuses for manufacturing the metallic fine particles are as follows:
(a) Evaporation Type as shown in FIG. 5
A heater coil (31) melts a metal mass contained in a crucible (32) and causes same to evaporate. As ambient atmosphere therearound, an inert gas is sealingly introduced from a cylinder (33) into an overall casing (34) in which the evaporated metal is made into fine particles. A collector (35) is provided for withdrawing the metallic fine particles supplied thereto on the inert gas flow.
(b) Arc-Discharge Type As shown in FIG. 5.
Arc discharge between a pair of electrodes (41a),(41b)melts a lump of metal (M). As ambient atmosphere therearound, hydrogen from a cylinder (42a) and an inert gas from another cylinder (42b) are sealingly introduced into an overall casing (43) in which the melted metal is made into fine particles, as the hydrogen as once activatedly dissolved thereinto in high concentration in the arc-discharging process is again expelled and discharged therefrom as supersaturant in the deactivated normal condition. A collector (44) is provided for withdrawing the metallic fine particles supplied thereto on the gas flow.
However, both these conventional types of apparatuses (a),(b) have drawbacks in that they are batchwise in their operation as to the material metal and that treating or handling in large amounts is difficult and impractical since they are based on the principle of metal evaporation or hydrogen discharge, in either case of which the speed is rather categorically restrained by the controlling factors of temperature and pressure.
In view of the actual status as above, this invention has as its object to provide an apparatus capable of manufacturing the metallic fine particles in a continuous and mass-production process.
To attain the object, the apparatus for manufacturing metallic fine particles is according to this invention characterized in that:
the arc-discharging section(s) is(are) provided within a hollow interior cavity in a high-speed-driven type rotary body, PA1 in a peripheral portion of the rotary body, radially outwardly of the arc-discharging section(s), there is(are) defined fine radial through hole(s) for centrifugally discharging therethrough the melted metallic material, PA1 radially outwardly of the rotary body, there is disposed, to define a confined space therebetween, an encasing stationary peripheral wall which is provided with a foced cooling means and which functions to cause the melted metallic material, as has discharged through the fine hole(s), to impinge thereagainst and to thereby be made into fine particles, and PA1 in the peripheral wall, there is provided a passage in communication with the space between the rotary body and this wall, thus with an inlet opening to the space, for withdrawing therethrough the metallic fine particles.
a passage is provided for supplying therethrough the metallic material to the arc-discharging section(s) when the rotary body is driven in rotation,
Function and merits accruing from the characteristic construction as above may be summarized in the following two items:
(1) The metallic material is supplied either fully continuously or somewhat intermittently through the supply passage to the arc-discharging section(s). As the material is melted there, it is made possible to centrifugally be ejected out at a high speed in a continuous way through the fine radial through hole(s) towards the peripheral wall in rotational angular distribution all over the entire wall periphery. Upon impingement against the forcedly cooled peripheral wall, the melted material is crushed into fine particles while being solidified at the same time. Thusly formed metallic fine particles may then be continuously withdrawn through the withdrawal passage. In this way, it is hereby made possible to realize practical continuous manufacturing of metallic fine particles, which has has been impossible with the convention apparatuses.
(2) Quite large centrifugal force on account of high speed rotation is available as the motive power for forcibly thrusting the melted material through the fine radial through hole(s). It is therefore possible to provide the radial through hole(s) in quite small diameter size and even then securely effecting therethrough the melted material at quite a high speed. As the melted material is thus crushed into fine particles upon vigorously shocking impingement against the peripheral wall, it has now been made possible to realize mass production of the metallic fine particles, or rather even ultrafine particles of less than 1 micron particle size.
In further conclusive expression, it is hereby made possible to complete an apparatus of enormous practical value as can manufacture, in continuous processing and with an innovatingly enhanced treating capacity, the metallic fine particles of extremely minute particle size, which are the focus of attention in recent years in quite a wide variety of industrial fields as the latent very useful material.
In a preferred embodiment of the apparatus for manufacturing metallic fine particles according to this invention, the rotary body has its lower peripheral portion in downwardly widening truncated conical slant shape to provide a smooth outgoing passage to the inlet of the withdrawing passage or near the same. Withdrawal of the product metallic fine particles is hereby made yet further smooth.
Still further preferred embodiments of the apparatus for manufacturing the metallic fine particles according to this invention and the advantages accruing therefrom will be apparent from the detailed description to follow hereunder.